This invention pertains to a fluid-pumping system employing an air-driven pump, which may be a double-diaphragm pump, and employing at least one pulsation dampener to dampen pressure pulsations at an outlet of the air-driven pump.
In fluid-pumping systems, pressure pulsations are known to occur in fluids being pumped. It is known to employ pulsation dampeners to dampen such fluctuations. Such pulsations are known to occur even if air-driven pumps are employed, whether single-diaphragm pumps, double-diaphragm pumps, or piston pumps.
One example of a pulsation dampener is disclosed in U.S. Pat. No. 4,979,441. The pulsation dampener disclosed therein employs an inner, perforated tube, an outer, rigid tube, and an intermediate, elastomeric sleeve. Gas pressure in a space between the outer, rigid tube and the intermediate, elastomeric sleeve dampens pressure pulsations in a fluid being pumped through the inner, perforated tube. With the pulsation dampener disclosed therein, it is difficult to compensate for minute losses of gas pressure in the space between the outer, rigid tube and the intermediate, elastomeric sleeve.
This invention provides a fluid-pumping system comprising a pump having an inlet and an outlet and a pulsation dampener arranged to dampen pressure pulsations at the outlet. The pump is arranged to be driven by air delivered to the pump at a regulated pressure. The pulsation dampener is arranged to be charged by air delivered at a regulated pressure via a pressure-reducing regulator, which is arranged to regulate the air pressure in the charging line by reference to the average pressure of the air driving the pump.
Preferably, the pressure-reducing regulator is arranged to regulate the air pressure in the charging line to a selected differential above or below the average pressure of the air driving the pump. In a preferred embodiment, wherein an averaging tank is connected to a driving line, via an orifice, the pressure-reducing regulator is arranged to regulate the air pressure in the charging line by reference to the air pressure in the averaging tank. The fluid-pumping system may comprise two pulsation dampeners, i.e., one arranged to dampen pressure drops at the outlet and another arranged to dampen pressure surges at the outlet.
Preferably, each pulsation dampener comprises an air-side chamber, which is adapted to be charged through the charging line, a fluid-side chamber, which is adapted to communicate with the outlet conduit so that the fluid pumped through the outlet conduit can enter the fluid-side chamber, and an elastomeric diaphragm, which is mounted so as to separate the outer and fluid-side chambers. Preferably, each pulsation dampener comprises two apertured walls, between which the diaphragm is mounted. One said wall is mounted so as to limit displacement of the diaphragm in a direction to decrease the volume of the air-side chamber and, thereby, to increase the volume of the fluid-side chamber. The other wall is mounted so as to limit displacement of the diaphragm in a direction to increase the volume of the air-side chamber and, thereby, to decrease the volume of the fluid-side chamber. Preferably, outside said one wall, the air-side chamber has a volume at least three times larger than the volume between the apertured walls.